Heatwaves here to stay

Heatwaves of the kind that killed 30,000 people in Europe last year will become more frequent, more intense and longer-lasting, according to reports by US scientists today.

Gerald Meehl and Claudia Tebaldi of the US national centre for atmosphere research (NCAR) report in the journal Science that the predicted increase in heat-absorbing greenhouse gases over the next hundred years is likely to intensify the pattern of heatwaves established in Europe and North America.

Computer models show that heatwaves will become more severe in the south and west of the US and the Mediterranean.

"It's the extreme weather and climate events that will have some of the most severe impacts on society as climate changes," said Dr Meehl.

The study backs up a prediction made by Swiss scientists, earlier this year that 2003 was a "summer of the future" for Europe.

Without some relief from the sweltering conditions, the elderly and the ill become increasingly at risk of heatstroke, heat exhaustion and dehydration. The team focused on Paris and Chicago be cause both had experienced lethal heatwaves in recent years.

The researchers predict that without worldwide cuts in greenhouse gas emissions, the average number of heatwaves in Chicago would increase by 25% to about two a year. The increase in Paris will be even greater, to an average of 2.15 a year.

The hot spells will also last longer. Heat waves in Chicago now tend to last for between five and eight days. Computer models predict that they could extend to eight or nine days.